1. Field of the Invention
The present invention relates to a spacer and an electron emission display including the spacer. More particularly, the present invention relates to a spacer that is configured to prevent electric charges from being accumulated on the surface thereof and an electron emission display including the spacer.
2. Description of the Related Art
Generally, electron emission elements are classified into those using hot cathodes as an electron emission source, and those using cold cathodes as the electron emission source. There are several types of cold cathode electron emission elements, including Field Emitter Array (FEA) elements, Surface Conduction Emitter (SCE) elements, Metal-Insulator-Metal (MIM) elements, and Metal-Insulator-Semiconductor (MIS) elements.
A typical electron emission element includes an electron emission region and driving electrodes for controlling the electron emission of the electron emission region. The electron emission region emits electrons according to the voltage supplied to the driving electrodes. The electron emission elements are arrayed on a first substrate to form an electron emission device. The first substrate of the electron emission device is disposed to face a second substrate on which a light emission unit having a phosphor layer and an anode electrode are provided. The first and second substrates are sealed together at their peripheries using a sealing member and the inner space between the first and second substrates is exhausted to form an electron emission display having a vacuum envelope.
In addition, a plurality of spacers is disposed in the vacuum envelope to prevent the substrates from being damaged or broken by a pressure difference between the inside and outside of the vacuum envelope.
The spacers are generally formed of a nonconductive material, such as ceramic or glass, and disposed to correspond to non-emission areas between the phosphor layers so as not to interfere with traveling paths of the electrons emitted from the electron emission device toward the phosphor layers.
However, when the electrons emitted from the electron emission device travel toward the corresponding phosphor layers, an electron beam-diffusing phenomenon can occur due to a high electric field caused by the anode electrode. The electron beam-diffusing phenomenon cannot be completely suppressed even when a focusing electrode is provided.
Due to the electron beam-diffusing phenomenon, some of the electrons cannot land on the corresponding phosphor layers but collide with the spacers. The spacers, formed of glass or ceramic, have an electron emission coefficient higher than 1. Therefore, when the electrons collide with the spacers, many secondary electrons are emitted from the spacers and thus, the spacers are positively charged. When the spacers are charged, the electric field around the spacers varies to distort the electron beam path.
The electron beam distortion causes the electrons emitted from the electron emission device to move toward the spacers. In this case, a visible spacer problem can occur where the spacers are observed on a screen by a user, thereby deteriorating the display quality.